Continuous steel making process



, B88881969 J. RAGUIN mL 3,486,882

CONTINUOUS STEEL MAKING PROCESS Dec. 30,"- 1969 v J, RAGUiN ET Af.'3,-4865882 CONTINUOUS STEEL MAKING PROCSS Filed July 23, 1968 2Sheets-Sheet 2 f ll United States Patent O Inf. C1. czlc /00, 7/00 U.S.Cl. 75-51 15 Claims ABSTRACT OF THE DISCLOSURE A method for continuouslyproducing steel in which a solid prereduced steel-forming material iscontinuously introduced into a refining vessel containing molten steeland slag while simultaneously and continuously introducing thermogenicmaterial and gaseous oxygen in such amounts into the refining vessel andthe molten mass therein that the amount of thermogenic material byexothermic reaction with the oxygen will insure melting of theintroduced prereduced solid steel-forming material and the amount ofgaseous oxygen is sufficient to convert said prereduced steel-formingmaterial into steel to thus obtain in the vessel a mixture of moltensteel and slag. The gaseous oxygen is introduced into the vessel fromabove in form of a jet so as to transform part of the mixture into ametal-slag foam which is continuously withdrawn by overow from thereuing vessel at such a rate that the amount of molten mass thereinremains substantially constant.

CROSS-REFERENCES TO RELATED APPLICATIONS The present application is acontinuation-in-part application of the application Ser. No. 515,807,filed Dec. 12, 1965 and now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to a processof making steel and, more particularly, the present invention isconcerned with a process of making steel which requires only one meltingof the steel-forming raw material.

The present invention is specifically concerned with making steel fromprereduced, solid, steel-forming `material.

It is an object of the present invention to produce liquid steel in acontinuous manner from prereduced solid, steel-forming material.

It is a further object of the present invention to produce steel fromsuch prereduced, solid, steel-forming rnaterials in a simple economicalmanner.

Other objects and advantages of the present invention will becomeapparent from a further reading of the description and of the appendedclaims, and it will be noted that according to the present inventioniron ore may be converted into steel without requiring the intermediateproduction of pig iron.

SUMMARY OF THE INVENTION With the above and other objects in view, thepresent invention relates to a method yof continuously producing steelcomprising the steps of continuously introducing into a refining vessel,containing a mixture of molten steel-forming materials, a solidprereduced steel-forming ice material at an elevated temperature belowthe melting point of the prereduced material, simultaneously andcontinuously introducing thermogenic material and gaseous oxygenrespectively in such amounts into the refining vessel and the molten`mass therein so that the amount of thermogenic material by exothermicreaction with the oxygen will insure melting of the simultaneously andcontinuously introduced steel forming material and that the amount ofthe simultaneously introduced oxygen is sufficient to convert thecontinuously introduced prereduced steel-forming material into steel tothus obtain in the vessel a mixture of molten steel and slag. Thegaseous oxygen is introduced in a jet from above into the mixture in therefining vessel to transform at least part of the mixture in therefining vessel into a metal-slag foam, and continuously withdrawing byoverflow the metalslag foam from the refining vessel at such a rate thatthe amount of molten mass in the refining vessel remains substantiallyconstant.

Within the context of the present specification and claims, the termprereduced solid material is intended to denote iron ores which havebeen submitted to a reducing treatment such that between about 40 and100% of the bound oxygen of the iron ore will have been removed by meansof reducing agents such as, for instance, carbon. If for the purpose ofproducing the prereduced solid material an excess amount of carbon orthe like is applied, such excess amount may be retained in theprereduced solid material which is introduced into the refining vessel.The other components of the iron ore and such also of the prereducedsolid material may vary greatly.

Process of manufacturing such prereduced solid materials are yvell knownin the art and are described for instance in a publication of CECA(Communaute Europeenne Charbon Acier), entitled Etude bibliographiquedes Procedes de reduction directe des minerais de fer, dated December1960. Therein, the DLM, Freeman, Wiberg and Finsider processes aredescribed.

The term thermogenic materials is to be understood, in the context ofthe present specification and claims, as denoting materials which reactin an exothermic manner with oxygen or oxidizing substances. The amountof thermogenic material which is to be simultaneously introduced withthe prereduced solid material, in accordance with the present invention,must be such that the heat requirements of the process are supplied bythe heat `provided by the enthalpy of the prereduced material, whichdepends on the temperature at which the prereduced material isintroduced into the refining vessel (which temperature preferably willbe an elevated temperature below the melting point of the prereducedmaterial), the enthalpy of the thermogenic material and the heat formedby oxidation of the same, and the combustion heat of gases which areoxidized during the refining process, primarily the combustion of COinto CO2.

Elements which form part of the thermogenic material and which may beoxidized in an exothermic reaction include, for instance, carbon,silicon and phosphorus.

The heat which is thus made available must be sufiicient to balance thethermic losses which correspond to the enthalpy of the slag, theenthalpy of the Withdrawn molten steel, the enthalpy of the gases, andother thermic losses due to radiation, etc.

According to various preferred embodiments of the present invention, theabove described process may comprise one or more of the followingfeatures:

(a) Prereduced steel-forming material may be introduced in the form ofpellets, generally having a size of between 2 and 40 mm. and preferablybetween l0 and 20 mm.

(b) The solid prereduced steel-forming material may be introduced inpulverulent form, for instance having a particle size of between micronsand 2 mm. and preferably having a particle size between 100 microns andl (c) The prereduced solid steel-forming material may be sponge ironand, preferably, the particle size of the sponge iron may be greatlyreduced and a pulverulent mass of sponge iron introduced into therefining vessel.

(d) A strongly thermogenic material such as, for instance, coke may beadditionally, simultaneously with the prereduced material, andcontinuously introduced into the refining vessel.

(e) The solid prereduced steel-forming material and the thermogenicmaterial may be jointly introduced into the refining vessel in the formof a mixture of these two types of materials.

(f) The thermogenic material may be introduced pneumatically inpulverulent form, for instance in the form of a pulverulent suspensionof thermogenic material in a suitable carrier gas.

(g) At least `a portion of the gas produced during the refining processwithin the molten metal mass in the relining vessel may be oxidized andburned by reaction with a portion of the oxygen introduced into themolten metal, before the gas reaches the upper level of the mass ofmolten metal in the refining vessel.

It will be understood, that the process of the present invention isprimarily concerned with a method of directly refining prereduced solidsteel-forming materials which are introduced in hot condition into arefining vessel wherein the prereduced solid materials are changed intoa liquid melt. These prereduced steel-forming materials may contain, inaddition to iron, tbermogenic elements such as carbon, phosphorus orsilicon in amounts sufficient to provide, upon reaction of thesethermogenic materials with oxygen, in part or fully the heat necessaryfor the melting of the material and for transformation of the same intosteel. If the amount of thermogenic materials contained in theprereduced solid material does not suffice for creating the amount ofheat required for the process then, as described further above,thermogenic materials are additionally introduced into the refiningvessel.

It is preferred according to the present invention to introduce thepredeuced, solid steel-forming material into the refining vessel, andinto the molten steel bath contained therein, in the form of pelletswhich, due to their geometrical shape, are particularly suitable forbeing introduced in a regular and controllable fiow so that within giventime periods the same amounts of prereduced, solid steel HY formingmaterial are introduced into the refining vessel.

According to another preferred embodiment, the prereduced, solid,steel-forming material is introduced in pulverulent form, by being blowninto the refining vessel suspended in a hot reducing gas. This isparticularly advantageous if the prereduced material is obtained inpulverulent form, for instance by iluidization processes known, per se,to those skilled in the art. The hot reducing gas serving as carrier forthe pulverulent, prereduced, steel-forming material may also be derivedfrom the waste gas leaving the refining vessel.

The present invention also contemplates, as discussed further above, thesimultaneous introduction of solid, strongly thermogenic materials,which, for instance may be carbon in the form of coke or graphite,phosphorus in the form of ferrophosphorus, silicon in the form offerrosilicon and aluminum in the form of ferroaluminum.

It is also within the scope of the present invention to reach a portionof the refining gas which develops in the metal bath immediately, andprior to escape of such refining gas from the metal bath, with oxygen soas to convert the refining gas to carbon dioxide, since thereby the heatcontent of the molten metal bath may be significantly increased.

The novel features which are considered as characteristic for theinventionl are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings inwhich the drawing is a schematic elevational view of an apparatus forcarrying out the present invention.

The invention will now be described by way of the following example withreference to the drawing without, however, limiting the invention to thespecific details of the example.

BRIEF DESCRIPTION OF THE DRAWING FIG. l is a schematic view showing an'arrangement for carrying out the method of the present invention; and

FIG. 2 is a view of an embodiment thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawing,reference numeral 1 indicates a heat insulated hopper made of refractorybricks and containing a relatively small amount of prereduced, hot,solid, steel-forming pellets which are introduced into hopper 1 in acontinuous manner from a conventional pelletizing device (not shown).The pellets may be produced in any conventional manner and producing ofthe pellets does not form part of the present invention.

From hopper 1, the mass of pellets is then continuously and evenlyintroduced through a refractory conduit 3 into a continuous refiningvessel 2 containing molten steel in its lower portion. The rate ofintroduction of pellets into a refining vessel 2 is controlled by meansof a conventional, revolving distributor wheel 4.

A stream of oxygen under pressure having pulverulent lime suspendedtherein is introduced into refining vessel 2 from above in form of a jetthrough lance 5 projecting into the reforming vessel and beingadjustable in vertical direction. It will be seen that although thenozzle of downwardly directed lance 5 is located above the upper levelof the molten metal, nevertheless, oxygen gas will be blown into theinterior of the molten metal mass- The thus introduced oxygen gas willassure the refining of the prereduced material and the excess heat ofthe refining reaction will bring about the melting of the pellets tothus form a mixture of refined metal and at least part of which istransformed by the oxygen jet into a slagmetal foam which passes byoverfiowing into portion 6 of the refining vessel in which the twophases, namely the slag and the molten steel, are allowed to separateinto a continuous metal phase and a slag phase fioating thereon. Themolten steel is then removed through an opening 7 located in the bottomof vessel portion 6, while the supernatant slag flows through an opening8 in the side Wall of vessel portion 6.

The pellets of pulverulent prereduced products which are introduced intothe left hand or refining portion of refining vessel 2 are preheated,prior to introduction into the vessel 2, preferably to a temperature ofabout 700 C.

and have the following composition:

Percent Fe, metallic 73.8 Fe, total 80.8 CaO 0.45 SiO2 3.6 MgO 1.8 A12030.9

10.0 Miscel. (P205, MnO) 0.35

118 standard cubic meters of oxygen carrying suspended therein 117 kg.of pulverulent lime, are blown into the refining portion of refiningvessel 2 through lance 5 per 1000 kg. of prereduced, solid steel-formingmaterial.

In this manner, raw steel is obtained having a temperature of 1600 C.and the following composition:

Percent 0.040 0.005

Thereby, an amount of 270 kg. of slag is formed per 1000 kg. ofprereduced steel-forming pellets, which slag has the followingcomposition:

C P S M According to FIG. 2 a lance 11 is provided in the vicinity oflance 5 for the purpose of introducing into refining vessel 2 asuspesnion of a mixture of prereduced steel-forming material in form ofpulverulent sponge iron and of thermogenic material the latterconsisting, for instance, of a mixture of pulverulent coke andpulverulent ferrosilicon containing 90% silicon.

It is obvious that the lance 11 could be used in the arrangement of FIG.1 to introduce separately the thermogenic material in pulverulent form,and that any combination of introducing means of the prereduced materialand thermogenic material is possible. For instance pulverulent cokecould be introduced through lance 11 and ferrosilicon in grains andprereduced ore through hopper 1.

The gases which are formed in refining vessel 2, and particularly in theportion thereof into which lances 5 and 11 extend, are withdrawn throughue 9. An additional lance serves for introducing oxygen into theinterior of vessel 2, again above the reacting mass of prereducedmaterial, for the purpose of causing at least partial co1nbustion ofcombustible refining gases emanating from the molten turbulent metalmass in the left hand portion of the refining vessel.

Pulverulent sponge iron which is introduced into the left hand ofrefining vessel 2. is preheated, prior to the introduction in thevessel, preferably to a temperature of about 750 C. and has thefollowing composition.

The gases which escape from the refining vessel and which are subjectedto partial combustion by means of the oxygen from lance 10 have atemperature of 1600 C. and consist of 21.9% CO2 and 78.1% CO.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can 'by applying current knowkledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constituteessential-characteristics of the generic or specific aspects of thisinvention and, therefore, such adaptations should and are intended tolbe comprehended within the meaning and range of equivalence of thefollowing claims. Y

What is claimed as new and desired to be secured hy Letters Patent isset forth in the appended claims:

1. A method of continuously producing steel comprising the steps ofcontinuously introducing into a refining vessel containing a mass ofmolten steel and slag a solid prereduced steel-forming material at anelevated temperature below the melting point of said material;simultaneously and continuously introducing thermogenic material andgaseous oxygen respectively in such amounts into the refining vessel andthe molten mass therein so that the amount of thermogenic material byexothermic reaction with the oxygen will insure melting of thesimultaneously and continuously introduced steel-forming material andthat the amount of the simultaneously introduced oxygen is sutlicient toconvert the continuously introduced prereduced steel-forming materialinto steel to thus obtain in the vessel a mixture of molten steel andslag, said gaseous oxygen being introduced in a jet from above into thematerial in the refining vessel to transform at least part of themixture in said refining vessel into a metal-slag foam; and continuouslywithdrawing by overfiow said metal-slag foam from said metal refiningvessel at such a rate that the amount of molten mass in said refiningvessel remains substantially constant.

2. A method as defined in claim 1, wherein said metal slag foam iswithdrawn into a decanting vessel and including the steps of causing insaid decanting vessel separation of said metal-slag foam into acontinuous metal phase and a slag phase fioating thereon, and separatelydischarging in the slag phase and the continuous metal phase from saiddecanting vessel.

3. A method as defined in claim 2, wherein said thermogenic material isselected from the group consisting of carbon, ferrophosphorus,ferrosilicon and ferroaluminum.

4. A method as defined in claim 3, wherein said thermogenic material iscoke.

5. A method as defined in claim 3, wherein said thermogenic material iscontinuously introduced into the refining vessel admixed to saidprereduced material.

6. A method as defined in claim 3, wherein said thermogenic material iscontinuously introduced into said refining vessel in the form of apulverulent suspension thereof in a carrier gas.

7. A method as defined in claim 6, wherein said carrier gas with saidthermogenic material in pulverulent form suspended therein is blown in ajet from above into said mass of molten material in said refiningvessel.

8. A method as defined in claim 2, wherein said solid prereducedmaterial is continuously introduced into said refining vessel in theform of pellets.

9. A method as defined in claim 8 wherein said pellets containthermogenic material insufficient amount to provide the heat necessaryfor the melting of said pellets and for their transformation into steel.

10. A method as defined in claim 2, wherein said solid prereducedmaterial is in pulverulent form.

11. A method as defined in claim 2, wherein said solid prereducedmaterial is sponge iron.

12. A method as defined in-fclaim 2, wherein oxidiza- Ible gas is formedduring transformation of said solid prereduced material into steel,andfwherein at least a portion of said oxidizable gas is reacted withoxygen while still below the upper level of said mass of molten steel insaid refining vessel.

A method as defined in claim 2, whffrpin combustible gas is formedduring transformation of said solid prereduced material into steel, andwherein at least part of said combustible material is reacted withoxygen while still'below the upper level of said mass of molten steel insaid refining vessel, Iand wherein the amount of oxygen introduced intosaid refining vessel is sufiicient to oxidize said thermogenic materialand said portion of said cornbustible gas.

14. A method as defined in claim 2, wherein said jet of gaseous oxygenis introduced into said refining vessel through a lance orifice locatedin said refining vessel directed towards and upwardly spaced from saidmass of molten steel.

15. A method as defined in claim 14, wherein said distance of said lanceorifice from said molten lmass of material in said refining vessel isadjustable.

(References on following page) References Cited UNITED STATES PATENTSHalley 75-52 Morrill 75-*60 X Kalling et al. 75-51 X Madaras 75-43 XMuller et a1 75-60 8 L. DEWAYNE RUTLEDGE, Primary Examiner G. K. WHITE,Assistant Examiner U.S. Cl. X.R.

